Electric furnace.



F. J. TONE.

ELEUTRIG FURNACE.

APPLICATION FILED MAR. 26, 1912.

1,954,3271 Patented Feb. 25, 1913.

WITNESSES INVENTOR ing greater uniformity, greater economy of UNITED sArs n1 FRANK J. 'ro'NE, or NIAGARA FALLS, NEW YORK, AssIGNoR TO THE CARBDRUNDUM COMPANY, or NIAGARA r LLs, NEW YORK, A CORPORATION or PENNSYLVANIA.

- ELECTRIC FURNACE.

I Specification of Letters Patent.

Patented Feb. 25.191

Application filed March 26, 1912. Serial No. 686386.

To all whom; it may concern: Be it known, that I, FRANK J. TONE, a resident of Niagara Falls, in the'county of l \iagara and State of New York, have infiivented a new and useful Improvement in Electric Furnaces, of which the following is a full, clear, and exact. description, reference being had to the accompanying drawings, forming part of this specification, in which Figure l is a vertical cross section showing a preferred form of furnace constructed in accordance with my invention; and Fig. 2 is a horizontal sectional view of the same. My invention relates to furnaces employed for the conversion ofshaped articles into silicon car-bid, such, for example, as the articles obtained in the process described in United States Letters Patent No. 992,698, issued tome on May. 16, 19,11. In such processes, molded articles of silicon carbid and carbon are buried in the mixture of silica and carbon and subjected to a temperature sufficient to form silicon-containing vapors, which penetrate the molded articles and convert theminto solidarticles of substantially pure siliconcarbid. In such processes as-heretofore practised, the majority of the energy supplied was consumed in con-verb. ing the enveloping mixture of silica and carbon into sil'iconcarbid, a relatively small jamount of the energy being available for the desired work "of silicidizing the articles to be treated. In other words, such furnaccs have had a very small capacity in proportion to the power used. Furthermore, uniform radiation from the resistance core into the article being treated was not oblaincd and the-articles were subjcc iid to displacement andother difficulties.

lVlyinvention is designed tobetter equalize, the te 'npcrature throughout the-conversion or silicidizing zone and to arrange the furnace so that more of the power .will be consumed in the silicidizing. action, givenergy consumption, and more satisfactory operating conditions.

In. the drawings, in which I show one form of furnaceconstructed in accordance with my invention, 2 represents the base; 3, 3 thehead Walls; and 4, 4 the side walls of the furnace, which is preferably of boxlike form open at the top.

' The carbon electrode terminals are shown at 5, 5, extending through the head walls and suitably connected to the source of'electrical energy.

The resistance cores are shown at 6, these being shaped so that the vertical dimension is much greater than the horizontal dimenslon, thus giving a more uniform horizontal radiation of heat from the sides of the core into the conversion zones, which are substantially parallel and equidistant from it.

..lhese cores are preferably made of granular carbon, though other suitable resistance material may be used, and they may be of block form or other solid shapes, if desired, By reason of elongating the resistor vertically, I am enabled to utilize a 'much greater proportion of the energy radiated than with a circular core. The amount of energy radiated uselcssly upwardly and downwardly is greatly lessened on account of the small amount of surface, as compared with that at the sides of the resistor.

The silicidizing zones are shown at 7, these being charged, for example, with molded articles to be converted, mounted on suit-able supports 7. These articles are 'placed in a vertical pile, the sides of which are preferably substantially parallel with and equidistant from the cores. The thickness of the conversion zone is so proportioned that a good conversion will be obtained throughout the zone, this being determined by trial by varying the energy output and the time of treatment. It will, of course, vary withditl'ercnt compositions. The articles to be treated are preferably provided with separators of carbon or other material, to permit a better permeation of ll'usilicon vapors, and (are shouldbe exercised in separating them lcngthwisoot the core, in order to reduce as far as possible the formation of leakage paths for the current.

- It is also desirable lo form the corresponding breaks in the support, in order to prevent leakage through the base of the fur nacc.

8 represents the embedding mixture which preferably consists of thirty parts pulverized coke, sixty parts silica sand and seven parts sawdust. This preferably entirely surrounds the-coreand ill! articles to be treated, exceptthat the latter may-be supported from the base of the furnace. By this arrangement, the articles will beltcrpreserve their shape and keep a constant pos1 icon-carbid furnace,

sition during treatment, as there is apt to be settling and displacement of the cores.

The proportioning of the cores and the "urnace dimensions will preferably follow he practice in the well known granular-core the principles of silicidizing zone only up to the point of formation of amorphous silicon carbid, if the time of treatment is properly extended, the carbon articles will be converted into amorphous silicon carbid. When a denser form of silicon carbid is desired, the operation is carried to thesp'oint where the entire space between the cores is brought above the temperature necessary for the formation of crystalline silicon carbid. After the operation has continued for a sufiicient time to give the desired degree of conversion, the furnace is shut down, allowed to cool and then unloaded. The upper and lower tiers of materials may be re-treated, if they do not show thedesired degree of conversion.

It is important that the surrounding mixture shown at 8 should be sufficiently porous to permit free circulation of silicon-containing vapors, and in place of using sawdust or similar material for such purpose, it is pos-v sible to use the silica and carbon in coarser lumps or a mixturet-hereof in briquet form. l. have also found in certain cases that the addition of silicon carbid to the silica carbon mixture will give improved results. In such cases, this reduces the shrinkage and settlement of the mixture, aids in the conduction of heat from the cores to the silicidizing zones, and has certain other advanarr-anneal;

When treating carbon articles and carrying the temperature of the The resulting arti-' the articles to be treated, without departing from my invention.

The novel process herein described forms the subject-matter of a divisional application Serial No. 7 32,879, filed Nov. 22, 1912.

I claim:

1. An electrical resistance furnace, having a carbon resistance core disposed for maximum radiation alongits vertical surfaces, means for supporting articles to be silicidized in a zone substantially parallel with said vertical surfaces, and a silicidiz ing envelop surrounding the articles;

2. An electrical resistance furnace, having a carbon resistance core disposed for maximumradiation along its vertical sur-. faces, means for-supporting articles to bc silicidized in a zone substantially parallel with said vertical surfaces, and an envelop surrounding the articles and capable of giving off silicon-containing vapors to the articles to be silicidized.

3. An electrical silicidizing furnace, having a plurality of carbon resistance cores disposed for maximum radiation along their vertical surfaces, means for supporting articles to be. silicidized in zones alternating with the cores and substantially parallel therewith, and a si'licidizing envelop surrounding the articles.

4. An electrical silicidizing furnace, having a plurality of carbon resistance cores disposed for maximum radiation along their vertical surfaces, means for supporting articles to be silicidized in zones alternating with .thecores and substantially parallel therewith, and a porous mixture containing silicon and carbon surrounding and extending between the cores. and articles.

5. An electrical silicidizing furnace, having a plurality of carbon resistance cores disposed for maximum radiation along their vertical surfaces, means for supporting articles to be silicidized independently of the cores and in zones alternating with the cores and substantially parallel with and equidistant therefrom, a porous mixture containing silicon 'carbid, silica, and carbon surrounding and extending between the cores and articles.

In testimony whereof, I have hereunto-set my hand.

' v FRANK J. TONE.

\Vitnesses:

A. I. FRANCIIOT, LESORF. (J. Invixr. 

